Abstract: A compressor including a cylinder, the cylinder delimiting a compressor chamber having a circular cross-section and the cylinder having a longitudinal axis and including a front wall, the front wall of the cylinder having inlet and outlet openings for passage therethrough of a medium to be compressed; and a reciprocating piston disposed in the compressor chamber, the reciprocating piston being reciprocable within the compressor chamber in a movement that includes a dead center position and having a pair of opposed ends with one end being more proximate to the front wall of the cylinder than the other opposed end and the reciprocating piston having an expulsion projection on its one end, the expulsion projection entering the outlet opening in a dead center position of the reciprocating piston, the longitudinal axis of the cylinder extending through the outlet opening.